Myopia is a disorder in which the eye is relatively long for the power of the cornea and lens resulting in blurred vision. Because myopia is the most common eye condition in the world, it is an enormous public health problem with a large economic impact on the population at large. Its contribution to acquired blindness varies from 3-19% depending on the study. Although very common, nothing secure is known about its pathogenesis despite studies of various animal models. A number of different studies provide compelling evidence indicating that myopia is inherited. The complexity of the genetics of this disorder requires a broad based collaborative effort to adequately locate the gene(s) for this disorder. The goal of this proposal is to contain the loci responsible for this disorder. Using uniform clinical criteria, pedigrees affected with myopia will be collected from two separate geographic regions. Blood samples from suitable families will be collected for DNA extraction which will be used for genetic mapping. Microsatellite repeat markers located at 10 cM intervals through the genome will be used for genotype generation. The genotype data will be utilized to create databases for linkage analysis. Potential areas suggestive of linkage will be further examined with additional markers from the potential region. The results of this investigation will (1) identify specific genetic loci for myopia, (2) permit an estimate of the relative importance of environmental exposure on myopia, and (3) provide a more rational framework for the classification of myopia based on genetic locus. Findings from this study may also provide further understanding of the pathogenesis of myopia and may have public health implications if there are some segments of the population in which preventing environmental exposures may alter the onset of disease or its further progression. This will have an even greater relevance if we are successful at defining the refractive component(s) of the eye which is responsible for the development of myopia.